ECM / PCM failures

I had an interesting conversation today regarding ECU failure rate. I'm wondering how may users have experienced ECU failures and what year had the highest failure rate. Our company make the Space Shuttle ECU which has never failed in flight but doesn't operate nealy as often as a typical car ECU. eace:

my ecu failed, but only because my engine died going through 4.5' of water and it sat there for 15 min. waiting to get pulled out so the ecu was filled with water and shorted out. It's a 98 classic, auto. I replaced it with a used one and it's worked fine every since.

SleeperXJ said:

I had an interesting conversation today regarding ECU failure rate. I'm wondering how may users have experienced ECU failures and what year had the highest failure rate. Our company make the Space Shuttle ECU which has never failed in flight but doesn't operate nealy as often as a typical car ECU. eace:

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How does the space shuttle decide ECU fail? And how much does it actually compute? The last I read up on it it was a very redundant system, only controlling what must be controlled with a computer, the rest being controlled by normal aviation style buses.

I have never replaced an ECU, and the only people I know who have did so only to have it turn out to be a different problem.

The computer on the XJ is generally very reliable. Yes, like anything else electrical, it can fail.

The computer is mistakenly blamed for many problems. I have read many posts I've read from people that have a problem; spend about an hour working on it, perform no testing and proclaim that the "computer must be bad". Only to order a new one to find out that it isn't. Many computers that are returned in an exchange test out perfectly fine.

My strategy for replacing the computer is one of "diagnosis of exclusion". Which means that everything else must be ruled out by testing before I even consider swapping out the computer.

wolfpackjeeper said:

How does the space shuttle decide ECU fail? And how much does it actually compute? The last I read up on it it was a very redundant system, only controlling what must be controlled with a computer

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The system that I worked on (not shuttle) had multiple processors. If the two main processors disagreed, the third processor would cast the deciding vote. How much it computes / controls is much less than a modern auto ECU. Flight ECU failures are captured via normal telemetry, in other words the flight ECU throws codes.